Antioxidant activity of N-acyl chitosan oligosaccharide with same substituting degree.

N-Maleoyl chitosan oligosaccharide (NMCOS) and N-succinyl chitosan oligosaccharide (NSCOS) were prepared by acylation with maleic anhydride and succinic anhydride, respectively. Their structural changes were confirmed by Fourier-transform infrared (FT-IR) spectroscopy and their substituting degrees were determined both as 0.49 by conductometric titration. Their antioxidant activities were evaluated by scavenging superoxide anion O(2·)(-), hydroxyl radical ()OH and determination of reducing power. The 50% inhibition concentrations (IC(50)) of NMCOS and NSCOS scavenging effect on O(2)(·-) were 2.25 and 3.27mg/mL, respectively. The IC(50) of NMCOS scavenging effect on (·)OH was 0.24mg/mL, however, at the same concentration determined, the value of NSCOS on (·)OH was 30.5%. The reducing powers of NMCOS and NSCOS at the concentration of 2.40mg/mL were determined as 0.46 and 0.41, respectively. The above results showed that NMCOS has better antioxidant activities, which may be related to the fact that maleoyl has stronger electron-withdrawing effect than succinyl.